1. Field of the Invention
The present invention relates to anaerobic curing impregnation sealant compositions, which are readily separable from water. More particularly the present invention relates to anaerobic curing impregnation sealant compositions which have a density. sufficiently different from water to allow facile separation therefrom.
2. Brief Description of Related Technology
Inpregnation sealing of porosity in porous parts frequently is carried out by introducing sealant compositions into the porosity under a pressure differential, by vacuum techniques which are well known in the art.
Sealant compositions typically employed in these impregnation applications include a wide variety of self curing anaerobic sealants, e g. the compositions described in U.S. Pat. Nos. 3,672,942 (Neumann); 3,969,552 (Malofsky); Re. 32,240 (DeMarco); and 4,632,945, which are curable through free radical polymerization in the presence of suitable free radical initiators, e.g., peroxy type initiators, as well as thermal curing sealants, e.g., the compositions described in U.S. Pat. Nos. 4,416,921 (Dunn) and 4,147,821 (Young), as well as sealants which cure by both anaerobic and heat cure mechanisms.
Impregnation sealant compositions are typically impregnated into the porosity of porous parts by vacuum and pressure techniques. A vacuum removes air from the porosity of the metal parts. Sealant compositions are then introduced into the porosity under a pressure differential using ambient pressure or elevated pressure conditions. After impregnation, an operation, such as a centrifuge operation, removes excess surface sealant from the metal part. Even after removing gross surface accumulations of the sealant, a significant amount of sealant remains on the surface of the porous parts, particularly in the vicinity of the pores. When the sealant is an anaerobically curable one, the surface accumulations as well as the outermost layer of the sealant in the pores of the parts, particularly shallow surface pores, contact oxygen, so that surface quantities of the impregnate remains uncured or only partially cured.
Remaining surface sealant or sealant trapped in blind holes of the impregnated parts is typically removed in an agitated water rinse zone. The impregnated and water rinsed parts may be transferred to an activator zone in which the impregnated parts are contacted with a catalyst activator solution (in the case of anaerobic sealants curing) or passed to a tank containing hot water, e.g., at a temperature of 90xc2x0 C. to 150xc2x0 C. (in the case of heat curing sealants) to effect curing of the sealant material at the entrance to the pores in the parts. Thereafter, the impregnated parts may be transferred to a fial rinse zone for removal of the activator solution from the impregnated parts.
A variation of this impregnation system uses a heat-curing resin in place of the anaerobically-curing resin, whereby the activating and final rinsing steps previously described are eliminated in favor of a hot rinse final step. In the heat-curing resin impregnation system, after impregnation and rinsing of excess surface material, the parts are contacted with hot water at temperatures on the order of about 50xc2x0 C. to about 90xc2x0 C. to cure the impregnation resin. See U.S. Pat. Nos. 4,416,921 (Dunn) and 4,147,821 (Young).
Whether the resin is heat curing or anaerobic curing, the problem of excess resin in the rinse water exists. In the past, the problem has been dealt with through wastewater treatment process or systems. See U.S. Pat. Nos. 5,006,233 (Muisener), 5,135,663 (Newberth, III), 5,149,441 (Welch, II), 5,273,662 (Muisener) and 5,433,860 (Yosuda). The problem has been addressed through emulsifying the resin in the rinsewater for subsequent treatment. See e.g., U.S. Pat. Nos. 4,416,921 (Dunn) (heat-curing sealant composition which contains a polymerizable acrylic monomer, an azonitrile and an anionic or nonionic surfactant to render the composition self-emulsifying upon mixing with water) and 4,147,821 (Young) (heat-curing sealant composition which contains (meth)acrylic monomer, a polyfunctional acrylic monomer, and an emulsifier, aid in the rinsing of uncured sealant from the surface of a porous article).
In these impregnation compositions and systems, either organic solvents or specific surfactants are used to remove uncured sealant in a reasonable rinse time and/or specific multi-component sealant compositions are used to avoid excessive rinse times. While the ""921 patent and the ""821 patent discuss emulsifying the rinsewater-resin mixture, so doing does not render facile physical separation of uncured excess resin from the rinsewater.
Another approach to solving the problem of excess resin in the rinse water is disclosed by U.S. Pat. No. 5,518,632, which increases the specific gravity of the rinse water through the addition of a salt, which allegedly causes excess resin which is less dense to float to the top. This approach is limited to directly treating the water, as opposed to providing resin composition which addresses the problem.
Accordingly, it would be desirable to provide an impregnation sealant composition that could be readily separable from rinsewater in its uncured state.
The present invention relates generally to rinse water treatable impregnation sealant compositions. These compositions are free-radical curable, and upon mixing with water are separable therefrom. The compositions include (a) a (meth)acrylate component and (b) a free radical initiator, where the (meth)acrylate component has a density sufficiently different from that of water, thereby allowing for facile separation therefrom when mixed
In a particularly desirable aspect of the invention, the (meth)acrylate component has a density that is greater than water, thereby allowing for the (meth)acrylate component to separate from the rinsewater and collect as a lower portion of the flowable contents of a rinsewater tank.
The present invention provides compositions for sealing porous parts which have improved water separability, thereby permitting improved rinse water treatability and reduced rinsing requirements. Instead of requiring emulsification with the rinse water, the compositions of the present invention separate from the rinse water due to differences in density. Indeed, having a density sufficiently different from that of water, such as greater than water, allows for excess resin to settle to the lower portion of the rinse tank. This allows the resin to be drained off from the rinse tank, leaving rinse water with the tank, or decanting of the rinsewater away so as to allow removal of the excess resin from the lower portion of the rinse tank. The compositions of the present invention easily separate from the rinse water.
In particular, the present invention provides an impregnation sealant composition with improved water separability, thereby reducing the rinse cycle duration, and which improves surface cleanliness of the porous article by more readily separating the uncured impregnation sealant composition from the rinsewater and hence from the formerly porous article.
The present invention further provides a composition including as its curable component a (meth)acrylate composition which desirably has a density greater than water, thereby allowing for the (meth)acrylate component to separate from the rinsewater and collect as a lower portion of the flowable contents of a rinsewater tank.
In another aspect of the invention there is provided a method of separating uncured or excess resin from an impregnation rinsewater tank which method includes providing a curable composition having a (meth)acrylate component, the (meth)acrylate component having a density which is sufficiently different than water so as to allow separation of the curable composition from the rinsewater. Desirably the density of the (meth)acrylate component is sufficiently greater than that of water to permit phase separation, whereby the resin portion of the composition settles to the lower portion of the rinse tank and is easily removed, leaving the rinsewater behind for potential future use.
In another aspect of the invention there is provided a method of preparing a curable impregnation composition which separates into a substantially separate layer in the presence of water which includes combining a (meth)acrylate component and a free radical initiator component, whereby the (meth)acrylate constituents together having a density sufficiently greater or less than water to permit separation when combined with water.
In another aspect of the invention there is included a composition which contains a combination of monomers in which one or more monomers may be soluble in water, as well as at least partially soluble in another substantially insoluble monomer present. In such a case, that portion of the water soluble monomer which dissolves in the water insoluble monomer will be carried along with the water insoluble monomer as it separates from the water, i.e., sinks to the bottom due to a density greater than water, or floats to the water surface due to a lesser density than water. Thus, even substantially water soluble monomers, which would not otherwise be easily separated from water, can be separated and removed from water to the extent that they are solubilized in the water-insoluble monomer by the present invention in this matter.
Surfactants may optionally be added to further enhance the properties of the present inventive compositions and facilitate separation of monomer components from water.
The present invention will be more thoroughly understood after a reading of the section of the application entitled, xe2x80x9cDetailed Description of the Inventionxe2x80x9d.